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Tachometer not working on Yamaha F90LA

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  • Tachometer not working on Yamaha F90LA

    My Tach on an Alumacraft boat which has a 2012 Yamaha F90LA is not working. Already replaced tach. Checked battery voltage and is 13.54 off and 14.54 with engine running. Voltmeter shows signal getting to tach but it may not be right signal? Is there a harness on the engine I can check? This may be a loose wire issue. any help is appreciated.

  • #2
    Originally posted by Mackadoo View Post
    Voltmeter shows signal getting to tach but it may not be right signal?
    Are you checking the green wire coming from the key switch?

    here's some data from checking my (working fine) tach signal

    (obviously measuring Hz or AC is more meaningful that DC)

    Originally posted by fairdeal View Post

    OK. re F225TXRD, measuring Green Tach lead to ground

    Key on, engine off:

    DC reading ~290 mV
    AC reading 0 V (naturally)

    Engine idling, Yamaha tach reading "7" :

    DC reading 13.3 V
    AC reading unstable, "bouncing" from ~4.4 - 32
    Hz reading unstable ranging ~75 -82

    here's a video of the running test


    • #3
      No Green Wire

      I have a purple wire for IGN. Black ground. The tach light is dark blue and the light works fine. The Tach wire is grey. Problem is I'm a rookie with boat wiring. No green wire.


      • #4
        ok, do you have a Yamaha key switch?

        that has a bundled lead of red, yellow, black, and green wires w/ bullet connectors.

        Does the gray tach wire connect to the green wire from the keyswitch?


        • #5
          Below the cup holder on the drivers side, I did find the wires that go to the Tach. The green that comes from the engine is connected to the grey wire going to the tach.n the connection feels good and solid.


          • #6
            Tachometer Not Working Solved - Interesting

            I wanted to come back here and post the answer to my own question of a tachometer that just quit working. I replaced the tach because there was a signal coming through the engine wire leading to the tach. Did not work.

            So I took into Cabelas in Richfield WI and had them take a look. It turns out this situation is very rare but does happen. The engine relay sensor went bad and the engine only has 48 hours. Its Yamaha part # 60E-81950-00-00.

            People at Cabelas were excellent. Mark the service manager and Earl who is the tech there is a wiz. Had to call the Yamaha reps to get the answer though. So if you have a bad tach this is something to check.



            • #7
              Glad you got it fixed. It certainly IS interesting.

              And, to me, incomprehensible.

              Rodbolt, Boscoe - could you explain what failure of the main relay

              (is this also a combo fuel pump relay?)

              could result in the engine running normally - except that the tach doesn't work?


              • #8
                methinks either you did not tell us the motor would not start OR ya got snarked.
                all that relay does is provide 12V power for the pumps,injectors,ISC and ign system.
                at key off the ECU holds the relay ON after the engine quits and allows the ECU to reset the ISC.
                but the ECU generates the tach signal.


                • #9
                  I am with Rodnut on this one. If the motor was operating normally, and the only problem was that the tachometer was not operating, then I don't see the relay as having anything to do with the tachometer problem.

                  As long as the problem is fixed, drive on.

                  But no one else should suspect that if they ever have a tachometer problem that it is the relay that is the culprit. Might as well suspect that it is the lower unit.

                  Yamaha probably is the one being snarked in the form of paying for a new relay under warranty.


                  • #10
                    Sorry to bring up this old post, but we are experiencing something similar on one of our 2007 F60's. The tach was intermittent and now has stopped showing RPMs and always shows a '0'. We checked all of the wiring connections and all seem tight and good. Any thoughts? Thanks!